diff --git a/src/attr/_make.py b/src/attr/_make.py
index 7439dc2ad..e84d9792a 100644
--- a/src/attr/_make.py
+++ b/src/attr/_make.py
@@ -448,7 +448,7 @@ def _transform_attrs(
     attrs = base_attrs + own_attrs
 
     if field_transformer is not None:
-        attrs = field_transformer(cls, attrs)
+        attrs = tuple(field_transformer(cls, attrs))
 
     # Check attr order after executing the field_transformer.
     # Mandatory vs non-mandatory attr order only matters when they are part of
diff --git a/tests/test_hooks.py b/tests/test_hooks.py
index 6b3420639..4dcd35240 100644
--- a/tests/test_hooks.py
+++ b/tests/test_hooks.py
@@ -217,6 +217,22 @@ class C:
         assert "CAttributes" == fields_type.__name__
         assert issubclass(fields_type, tuple)
 
+    def test_hook_generator(self):
+        """
+        Ensure that `attrs.fields` are correctly recorded when field_transformer is a generator
+
+        Regression test for #1417
+        """
+
+        def hook(cls, attribs):
+            yield from attribs
+
+        @attr.s(auto_attribs=True, field_transformer=hook)
+        class Base:
+            x: int
+
+        assert ["x"] == [a.name for a in attr.fields(Base)]
+
 
 class TestAsDictHook:
     def test_asdict(self):